Reciprocating pump



Aug. 15, 1933. c. BROWN RECIPROCATING PUMP Filed Feb. 19, 1952 Z-Sheets-Sheet l e/ZZZbrnq gi.

- C'Zemenl' firown/ Aug. 15, 1933. c BROWN 1,922,121

RECIPROCATING PUMP Filed Feb. 19, 1952 2 Sheets-Sheet 2 Invenlbr Clai ant firown/ 29 Q haw-m :Ellfornqys Patented Aug. 15, 1933 PATENT OFFICE 1,szz,1z1

nncrmoca'rmo rum Clement Brown, Birmingham, England, ullgnortl) Amal Limited, Mum Kuhn Application Felll'llfl'! 1a, 193:, Serial No. 594,019,

and in Great Britain May 29, 19:1

1 Claim. (cl. 10H.)

This invention relates to gasoline or other fuel reciprocating pumps, particularly for supplying the carburetors of the internal-combustio engines of motor-vehicles or aircraft.

At the present time the operative pumping elements of such pumps are commonly diaphragms, but the diaphragms' tend to deteriorate after a longer or shorter period of running and to fracture, when leakage of fuel results. On. the other hand, with plunger-type pumps as heretofore proposed, it is almost impossible to prevent leakage past the plunger or piston.

The main object of the present invention is to provide an improved arrangement of plungertype pump in which any liquid leaking past the piston will be returned for further use..

A further object is to provide a passage connecting the interior of the pump cylinder, at a point away from the operative surface of the piston, to the inlet or suction side of thepump, this passage being available for taking of! any liquid that escapes from the pumping chamber in this passage will always be sub-atmospheric while the pump is operating, some such provision being necessary in those cases where there is a possibility of the pump being gravityfed temporarily, as, for example, when the car is on a steep hill or the aircraft is at such an angle that this might happen.

Furthermore, particularly in those cases where the operating means for the piston include an arrangement of springs by which the piston stroke becomes reduced as the pressure on the delivery side of the pump is built up, becoming negligible when the requirement for fuel ceases, it is found that there is a greater tendency in these conditions for the relatively high pressure on the delivery side of the pump, whilst the piston is substantially stationary, to increase the leakage past the piston. In accordance with a still further feature of the invention this difficulty is obviated by the'provision of an automatic valve in a bypass connected with the pump delivery.

In the accompanying drawings,

Figure l is a longitudinal section through one form of fuel pump according to the invention,

Figure 2 is a transverse longitudinal section thereof taken on the line IIH of Figure 1, and

Figure 3 is a diagram of connections, showing 55 a modification.

Like numerals indicate like parts throughout the drawings.

In the construction illustrated, in Figures 1 and 2 particularly, the main body of the pump is formed as a casting with a small vertical through passage 2 communicating laterally with a relatively large offset portion where the pump cylinder 3 is arranged with its axis horizontal. The offset portion terminates in a flange 4 for use in attaching the'pump to the engine or 6 elsewhere. The fuel is brought in through an inlet 5 on one side of the body into a depending cup-shaped casing 6, preferably of glass, which is clamped to the underside of the body in a known manner, and extending into this casing is a filter '7 supported by a cap 8 attached to a plug 9 which is screw-threaded externally to engage the lower end of the vertical bore 2 in the body or of means screwed thereinto. Disposed above the filter in the plug 9 isa seating 10 for an inlet ball valve 11 through which communication is established with the pump chamber 12 at the inner end of the cylinder.

Communicating with the upper end of the pump chamber is an outlet ball valve 13 leading to thefuel delivery pipe 14. The seating for the latter ball valve and the back stop for the inlet ball valve, with the appropriate passages. are formed in a plug or a plurality of plugs located in the vertical bore 2.

The pump cylinder is closed at its outer end by means of a cap 15 provided centrally with a tubular member 16, coaxial with the cylinder, which serves as a guide for the piston rod 1'1. The outer end of the piston 'rod (relative to the pump) is formed, with a head 18 which engages the driving cam 19, being urged towards the same by means of a compression spring 20 disposed around the guide for the piston rod and operating between the cap 15, or a lug 21 on the guide, at one end and the face of the head 18 away from the cam at the other.

The piston 22 is formed with a barrel portion extending substantially the whole length .of the cylinder. There is a hole in the centre of its operative surface which is closed by a plug 23 screwing therein andformed in the interior of the piston with a hooked arm 24 or the equivalent which engages behind a head 25 formed on the inner end of the piston rod. Thus, when the cam recedes from the piston rod and the return spring causes the piston rod to move outwardly, the piston (if fully advanced) is drawn away from the pump chamber. As the cam operates the piston rod in a driving direction,

the inner head of the latter moves clear of the hooked or like member on the piston. The operative stroke of the piston, however, is effected by means of a compression spring 26 disposed in the interior of the piston around the piston rod and operating between the piston and the cap 15. Thus, when the pump effort exceeds the requirements of the engine so that the pressure in the pump chamber builds up, the operating spring 26 tends to be held compressed and the piston stroke becomes reduced whilst the piston rod reciprocates more or less idly.

It should be noted that any fuel leaking between the piston and the cylinder walls would,

tend to find its way along the piston rod, and perhaps even into the engine. In order to avoid this, a passage 27 is provided, through the body of the pump, connecting the interior of the cylinder at a point away from the operative surface of the piston to the inlet or suction side of the pump, for example, to the upper end of the filter chamber. This passage may connect with the interior of the cylinder at one or more places. For example, the cylinder may be provided with a circumferential groove 28 on its inner periphery to which the passage leads, and, in particular, such groove may be arranged substantially midway along the length of the cylinder, as shown in Figure 1. However, this groove can be provided elsewhere in the cylinder; for example, at the end of the same away from the operative surface of the piston, if desired, as indicated in Figure 3, though, in this case, when the end of the passage 27 is not normally lapped by the barrel of the piston, there will be a tendency for air to be drawn from the interior of the piston when starting up the pump. Such an arrangement will, on the other hand, act satisfactorily in preventing fuel from leaking to the exterior of the pump.

In some cases, where the pump is drawing liquid from a reservoir which is only slightly below the pump when the vehicle or aircraft is more or less level, there may be a tendency for the reservoir to be raised above the pump when the car is on a steep hill or when the aircraft is at an appropriate angle, and in that case the pressure in the filter chamber would no longer be sub-atmospheric as the fuel would be gravity-fed to the same. In order that any liquid leaking past the pump piston shall be returned to the filter chamber, however, it is desirable that the pressure here should be maintained sub-atmospheric while the pump is operating. For this reason, therefore, use may be made of a loaded valve 29 or the like disposed in the inlet to the filter chamber, the same, for example, comprising a weighted or springpressed ball which has to be raised to allow the inlet of fuel, and the loading can be adiusted as desirable to ensure that the pressure in the filter chamber will always be sub-atmospheric.

Furthermore, the drawings show a bypass valve 30 arranged on one side of the central bore of the body opposite to the loaded suction valve 29 and both these valves are arranged to slide in vertical bores in the pump body which are co-planar with the central bore 2, this plane being at right-angles to the axis of the pump piston.

The bypass valve 30 is disposed between the delivery side of the pump and the supply tank, and for this purpose a passage 31 is provided through the pump body connecting the bypass valve with the delivery side of the pump, and there is aconnection 32 from the delivery side of the bypass valve to the upper end, of the fuel tank 33, this connection preferably consisting of a pipe 34 mounted alongside pipe 35 by which the fuel is delivered from the tank to the pump inlet 5.

The bypass valve is loaded so that in ordinary conditions it will remain closed to a greater or less extent to maintain substantially constant pressure in thedelivery system, but when the demand for fuel falls off and the pressure tends to build up on the delivery side of the pump it opens to a greater extent to allow excess fuel to be returned to the tank, so that the stroke of the piston is more or less maintained in any condition whilst the delivery pressure remains steady.

It will be seen that by means of the invention a simple form of plunger-type pump is provided in which the fuel being pumped is prevented from reaching the exterior of the pump or from entering the engine. As the pump always tends to deliver more fuel than is required, even a'very large leakage will not undermine the satisfactory operation of the pump.

What I claim as my invention and desire to secure by Letters Patent of the United States In combination, a pump casing having a cylinder with a downwardly inclined passage leading from the lower portion of the cylinder, a piston movably mounted in the cylinder with its leading edge disposed always forwardly of the mouth of the passage, a container below the casing and communicating with the lower portion of the passage, inlet and exhaust valves for the pump above and communicating with the container and also intermediately with the pump, a supply tank, a supply connection leading from a low portion of said tank and connecting with the container, a loaded check valve in the supply connection, a return connection coupled to the output side of the pump and to a higher level of the supply tank, and a loaded valve in said return connection.

CLEMENT BRQWN. 

